Abstract

Freshwater fishes are threatened by anthropogenic disturbances such as increased temperatures and turbidity. These abiotic stressors can have important impacts on behaviour, physiology and cognition, but how these stressors can interact with predation risk, a pre-existing biotic stressor, have yet to be explored. In this study, we experimentally exposed Trinidadian guppies (Poecilia reticulata) to increased predation risk and increased temperatures (experiment 1) and to increased predation risk and increased turbidity (experiment 2). This allowed for the exploration of the isolated and interactive effects of multiple stressors on neophobia, the fear of novelty, and learning of novel predator cues. Using a 2x2 design, guppies were exposed to high vs low levels of disturbance (temperature or turbidity) combined with high vs low levels of predation risk over one week. We then tested for their impacts on neophobia and learning. Guppies exposed to increased temperature and increased risk (experiment 1) in tandem displayed an increase in antipredator behaviours to a novel versus risky stimulus. However, in contrast, guppies exposed to increased turbidity and increased risk (experiment 2), both as single stressors or combined stressors, displayed increased antipredator behaviours to risky than novel stimuli. Surprisingly, individuals exposed to both increased temperatures and increased predation risk exhibited learning suggesting that learning of novel predator cues may convey a selective advantage under highly disturbed conditions. In contrast, guppies exposed to increased turbidity and/or increased predation risk in experiment 2 did not exhibit learning with perhaps turbidity lowering the perception of predation risk. Taken together, our findings suggest that interactions between abiotic stressors, namely temperature or turbidity, and predation risk can impact learning of novel predator cues, and to a lesser extent neophobia.